Study On The Synthesis Of O-Phenylphenol From Cyclohexanone

O-phenylphenol(OPP)is a fine chemical product which is widely used for the preparation of bactericides,preservatives,surfactants, intermediates of dyes,plastic stabilizers and fire retardants.Using cyclohexanone as a starting material,OPP can be prepared by a tow-stage process comprising the condensation of cyclohexanone to its dime and subsequent dehydrogenation of Dimer to OPP.This process is simple, economic and has been industrialized abroad.However,in China such unit has not been available in big and industrial scale.In this thesis the preparation of the OPP from cyclohexanone via the two-stage process was investigated.The study is focused on the preparation method of the dehydrogenation catalyst and the influence of alkali-metal salts on the catalytic performance.Firstly,condensation of cyclohexanone using acidic catalysts such as sulfuric acid and alumina was systematically studied.The result showed that Al₂O₃ owned a high activity and selectivity when it was adopted as the condensation catalyst,the conversion of cyclohexanoe was up to 74%, and the selectivity of Dimer reached 87%.Using Al₂O₃ as a catalyst has the advantages that separation of the catalyst from the liquid product and is easy,subsequent purification of the product is simplified.The Pt/γ-Al₂O₃ dehydrogenation catalyst was prepared by equal-volume impregnation usingγ-Al₂O₃ as the support,chloroplatinic acid as a precursor and K-salts as promoters to improve the catalyst performance.Factors that influence the performance of the dehydrogenation catalyst were investigated including the properties of the support,the amount of platinum supported,the type and amount of the promoters and preparation conditions.The results showed that the impurities in Al₂O₃ support had a significant influence on the catalyst performance.The content of SiO₂ should be lower that 0.3%and Fe₂O₃ should be lower than 0.1%.at 360℃to calcine the catalyst,With the amount of supported Pt of 0.5%(based the quality of the cartier),and K₂SO₄ as a promoter,the catalyst showed highly activity,selectivity and stability.The yield of OPP amounted 93%.Characterization using XRD, NH₃-TPD and CO₂-TPD revealed that the high OPP yield and stability of the catalyst with K₂SO₄ as a promoter is mainly due to the lower amount of the acidic sites on its surfaces.Optimization of the reaction conditions indicated that at T= 355℃,LHSV=0.2 h^-1,H₂=40ml/min,the catalyst showed its best performance.In the duration of 240h stability test,the average yield of OPP amounted 92%and no significant decrease in the activity was observed,indicating that the catalyst had a good stability.